You can during the 30 days trial and if you get caught with overage after the trial is iver they are supposed to terminate your existing vms. I don't know the particulars of it though.
While you're in the trial it is not super obvios what's always free and what's not. (I have a summary of it somewhere if anybody is interested.) There's also the problem of what to kill from the point of view of Oracle. You have VMs and you're over the limit on day 31. Which VM are they supposed to kill? I think they might be killing everything.
